1) Exactly said as above... probably power supply. With age, fatigue will kill your power supply and it might be time to replace it. Might also be dusty inside your PSU and might be good to clean it up... Most of the time, overheating will damage components, and will do exactly what you see... a component that stops working after a short amount of time, and takes an hour before working again sounds like an overheating problem... so i would clean the power supply throughly with compressed air before replacing it 1st... might also check your voltages inside your bios monitoring section and see if any voltages are out of specs...
2) Might be time to clean out your CPU fan/heatsink... dunno if you do clean your PC often, but i have seen messes of dust covering heat sinks on CPU coolers from some customers, that it's easy to see if a PC is over heating.
3) Last but not least: Busted caps on your motherboard. Start looking around for busted capacitors. This is a common problem theses days with companies trying to cut cost of their common components, they buy cheaper stuff, but it ends up to be crappy stuff that craps out very fast. A leaking capacitor starts doing random problems not too often, but when it leaked so much to the point of being visible, you are mostly getting the type of problem you are describing.